This pick is intended to drive a wedge into Republicans (do they take a "centrist" who is 180 degrees opposite of Scalia on gun rights) or wait for a Trump or Hillary pick? If he goes down, they use it as an issue in the election. If he goes through, Republicans are demoralized. I do not think it much of a surprise. Still, there is really no answer other than this:

He was part of the panel that got reversed on the SCOTUS Heller decision. The general consensus is he is not seeing an individual right under the Second Amendment (or certainly a much weaker one than what Scalia and the other conservative justices supported).